Prototypes for mechanical designs are used by engineers during product development. Engineers can test how a part will fit or operate by building a prototype. Prototypes can reveal things that were unanticipated by the designer. Some prototypes are made to as a miniaturized model so as to be less unwieldy or less expensive. Still, even miniaturized prototypes can be instructive to the designer or user. Prototypes can be used to test how a hand-held device will feel in the hands of a user. Prototypes can facilitate the development of a part that must interface with another part. For example a prototype may be given to a vender who has contracted making a part to which the prototype must couple.
Three-dimensional (3D) printing can be performed to produce prototypes of designs. 3D printers may use fused deposition modeling to deposit materials. In fuse deposition modeling, a part may be produced by extruding small diameter beads of liquid material that harden soon after deposition. 3D printers may use granular materials binding methods that selectively fuse materials in a granular bed. Layers of granules are added to the granular bed and the fusing process is then repeated. Lamination techniques have been used by 3D printers to adhere layers of paper or other material in layers. Photopolymerization has been used to selectively polymerize a bath of material. Where the bath experience a light of a certain intensity, polymerization occurs.